When a drizzle delayed the start of the third round, tournament officials decided Djokovic’s match should be played inside.

“I was a little bit surprised, when I saw sunshine, that the roof is closed,” Djokovic said. “Obviously they’re relying on a forecast that I don’t think is very reliable here. But OK.”

The No. 1-ranked Djokovic missed opportunities to seize an early lead, failing to convert his first five break-point chances before he lost serve at love to drop the opening set. But he dominated from there, breaking in the first game in each of the final three sets.

“I was a set down but managed to make the crucial break in the opening game of the second set,” Djokovic said. “And then I thought I played really well.”

The match remained entertaining even as it became lopsided. One game in the final set lasted 26 points and had Djokovic smiling at Stepanek’s unconventional style, which included a belly flop in pursuit of a shot.

“The fourth set from Novak’s side was very impressive,” Stepanek said. “I was battling until the end, but the fourth set I felt like no matter what I do on the court, he always answers.”

The victory made it two in row under the roof for Djokovic.

“I thought I played great,” he said. “But, look, this is an outdoor tournament, so I think everybody wants to play when the roof is open.”